1. Technical Field
The present invention relates to a linear guide with an integrated linear motor, in which the position of the movable element transversely to the drive direction can be actively affected, for example for correcting track deviations. Such linear guides are used for the exact positioning of objects.
2. Background Information
Advances in the field of microelectronics in particular make it necessary for objects, such as wafers or electronic components, to be positioned always faster and always more accurately. If it is intended in the course of this to provide a particularly low-friction seating of the movable elements, the employment of air-cushioned linear guides is known, in which the movable element is kept spaced apart from the stationary element by an air cushion. A linear motor, which provides the drive in the desired guide direction, can be integrated into such a guide. It is disadvantageous that such air-cushioned guides are not particularly stiff transversely to the guide direction, so that positioning transversely to the guide direction cannot be performed with the required accuracy.
WO 2007/024031 A1 describes a linear guide in which a movable platform is conducted in a contactless manner at a defined distance from a surface linearly along this surface. On the one hand, electromagnets at the four corners of the platform provide for the preloading of the bearing, on the other hand they are used for maintaining the distance from the platform constant, and in this way for compensating deviations perpendicularly with respect to the surface. However, a deviation perpendicularly to the guide direction and parallel to the surface cannot be corrected by this system.
WO 2007/026270 A1 describes an ironless linear motor, whose coils are arranged in the magnetic field of the stator in such a way that the linear motor can be used as a drive mechanism in two directions, which extend perpendicularly to each other. By this it is possible, for example, to advantageously operate a pick-and-place machine.
Position-measuring arrangements are known from DE 102005023984 A1 which have, besides an incremental track on a scale for measuring a displacement in one measuring direction, an additional incremental track, which can detect small displacements transversely to the actual measuring direction.